Coal enhancement process

ABSTRACT

The present process produces a clean burning coal from low grade coal and has a higher heating value per unit mass, as compared to the feed stock coal. The clean coal may be used in coal-fired power plants, industrial boilers, and homes since it produces fewer or none of the emissions commonly associated with coal burning devices. The process treats coal prior to its combustion and removes about 90 percent of the pollutants. These pollutants are removed within 6 to 18 minutes, many of which may be recycled into products such as roofing tar, chemical feed stocks, and light hydrocarbons that can be used as gaseous fuels. The final product is suitable for use in homes where coal is used for cooking and heating, and significantly improves the health of those who have previously been exposed to toxic fumes from burning uncleaned coal in their homes. The process is fueled by its own by-products, recycles heat, and reduces coal weight to save energy in transporting it to the user.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to the field of treating biomass toenhance its value or rank. More particularly, the invention concerns aprocess for the treatment of biomass, especially coal, to efficientlyconvert the selected feed stock from low rank into a high grade fuelcapable of increased heat release per unit of fuel. This is accomplishedin part by driving off most on the moisture trapped in low grade coal.The process simultaneously scrubs the coal of pollutants or impurities,many of which are organic volatiles, which are also referred to asby-products.

These by-products are largely combustible and can provide the heatenergy required to operate the inventive process after start up in amanner similar to that of a petroleum refinery refining crude oil toproduce clean fuels. The removed by-products are recycled into productssuch as roofing tar, and chemical feed stocks. The organic volatiles arelight hydrocarbons that can be used as gaseous fuels, first to power theprocess after startup, with the remaining organic volatiles beingseparately processed for other applications. The process further rendersthe coal into a low smoke generating fuel to make its use moreacceptable for domestic purposes such as cooking and home heating.Finally, the inventive process reduces the weight of the coal, whichreduces the cost to transport the treated coal to the location where itis burned as fuel.

The process is an energy conservation measure on several differentlevels. The process increases rank of the coal making it a moreeffective fuel, removes moisture, uses the by-products removed from thefeed stock to power the inventive process, produces treated by-productsfor other applications such as gaseous fuels that contain more usefulenergy, and reduces the weight of the coal to reduce energy consumptionin transporting the coal to its combustion site. The process alsorecycles heat to further lower fuel consumption in operating the processThe inventive process is principally designed for use withsub-bituminous and lignitic coal, but it is equally applicable tobiomass such as wood waste, shells, husks, and other combustiblematerial of organic origin.

2. Description of the Prior Art

Biomass is one of the largest and most readily available energy sourcesknown to man. Biomass is found in immature forms, such as wood, shells,husks and peat. Vast amounts of biomass are also available in the formof lignite, sub-bituminous, bituminous and anthracite coal. Man has beenreleasing the energy trapped in these materials ever since he discoveredand was able to control fire. The inefficient release of these vastenergy reserves, however, has resulted in a degradation of the qualityof the atmosphere and the environment, and some believe it contributessignificantly to global warming. The increasing demand for energy,created by man's insatiable appetite for the products made available byan industrialized society, have created a need to release this energy ina safe, clean and environmentally responsible manner.

It is known to treat coal with the application of heat in a controlledenvironment to increase its rank. The present invention is actually asignificant improvement over Hunt, U.S. Pat. No. 6,447,559. Hunt teachestreating coal in an inert atmosphere to increase its rank. In thepresent invention, coal is first heated to a temperature of 400° F. inan inert atmosphere to produce coal having only 2-5% moisture, thenheated in an inert atmosphere to 1500° F. to produce coal having only1-2% moisture and a mass reduction of up to 30%, to produce coal havingless than 2% moisture and a volatiles content of less than 25%, thencooling the coal in an oxygen-free and dry atmosphere, and finallycollecting it.

The prior art preceding Hunt had recognized that heating coal removesmoisture and enhances the rank and BTU content of the coal. It was alsopreviously recognized that this pyrolysis activity altered the complexhydrocarbons present in coal to a simpler set of hydrocarbons. Thismolecular transformation resulted in a more readily combustible coal,but an unstable product. The prior processes took several hours tocomplete, which made them slow and costly in both capitalization andproductions costs. Hunt greatly shortened the processing time of theprior art preceding Hunt.

But Hunt does not recognize either the use of by-products to power theprocess, or the ability to “farm” a great number of by-products forconstructive use outside of the process. Hunt is also a horizontalprocess, while the present invention is a vertical process that can takeadvantage at certain points of gravity is moving the coal from one zoneto another. Energy conservation is achieved by the present process onmultiple levels, and environmental conservation is achieved both in theprocess facility and by the cleaner burning coal after being processed.

SUMMARY OF THE INVENTION

Bearing in mind the foregoing, a principal object of the presentinvention is to improve upon prior art coal upgrading processes thatutilize heat and pressure to remove moisture and volatile matter fromcoal by minimizing the creation of unstable products that are prone tomoisture re-absorption, size degradation, and spontaneous combustion.

Another principal object of the present invention is to improve the rankof low grade coal by converting it into a high grade fuel capable ofincreased heat release per unit of fuel and doing so with theby-products of the process such as organic volatiles that are lighthydrocarbons that are fuel to power the process after startup.

Another object of the present invention is to improve the rank of lowgrade coal using a process that is energy conserving on several levels,i.e., the increased rank of the coal makes it a more effective fuel,removes moisture, uses the by-products removed from the feed stock topower the inventive process, produces treated by-products for otherapplications such as gaseous fuels that contain more useful energy, andreduces the weight of the coal to reduce energy consumption intransporting the coal to its combustion site.

A further object of the invention is to produce a clean burning coal byremoving pollutants so that burning the coal minimizes air pollutionrendering the coal a more environmentally acceptable fuel.

An additional object of the present invention is to render the coal intoa low smoke generating fuel to make its use more acceptable for domesticpurposes such as cooking and home heating by removing toxic pollutants.

A further object of the present invention is to reduce the inefficientrelease of energy reserves in the form of biomass such as coal to, inturn, reduce degradation of the quality of the atmosphere and theenvironment, and reduce global warming.

Another object of the present invention is to release biomass energy ina safe, clean and environmentally responsible manner.

An additional object of the invention is to provide places in the worldlike China having ever increasing energy needs with a way to utilize itssignificant coal deposits in a way that has a positive impact with othernations concerned with air pollution and global warming.

A related object of the invention is to provide nations like China whoalready use coal for heating and cooking in homes with a way to improvethe health of its citizens by minimizing smoke and exposure topollutants when burning coal in a home.

Other objects and advantages will be apparent to those skilled in theart upon reference to the following descriptions and drawings.

In accordance with a principal aspect of the present invention, aprocess produces a clean burning fuel from low grade coal. This cleanfuel is similar to coal, moisture resistant, stable, and has a higherheating value per unit mass, as compared to the feed stock coal. Theclean coal fuel may be handled and combusted like coal in coal-firedpower plants, industrial boilers, and homes; however, it produces feweror none of the emissions of harmful air pollutants that are commonlyassociated with coal burning devices. The inventive process treats coalprior to its combustion and removes about 90 percent of the pollutantsinherent in coal that are responsible for creating smog and unhealthyair.

These pollutants are removed within 6 to 18 minutes, many of which maybe recycled into products such as roofing tar, chemical feed stocks, andlight hydrocarbons that can be used as gaseous fuels. The final productis optionally formed into briquettes for use in homes where coal is usedfor cooking and heating. Because of their clean burning characteristics,the use of these briquettes significantly improves the health of thosewho have previously been exposed to toxic fumes from burning uncleanedcoal in their homes.

In accordance with a secondary aspect of the present invention, theprocess uses a different approach where it uses a multi-stage heatingprocess to gradually heat the coal under controlled residence times andatmospheres to produce a stable product with an increased BTUcontent—this is a unique and distinguishing aspect of this process overits competitors. The mix of gasses in each zone is proprietary to theinventive process and ensures that the coal loses its volatile matterwithout combusting itself to produce a clean coal fuel.

The apparatus is comprised of three chambers, each of which isconsidered a zone. Coal is gradually heated in the first two chambers(zones) and then cooled in the last chamber (zone). Each heating zonemay be viewed as a stand-alone partial gasification chamber. Coal isheated under controlled temperatures, residence time, and ambientpressure as it progresses through each zone. Process variables in eachzone are adjusted to suit desired end product specifications.

The feed stock coal is crushed to a typical size distribution forutility coal and fed into Zone 1. The temperature and residence time inthis zone is sufficient to remove surface moisture from the coal. Thecoal moves into the second zone where the temperature and retention timeare maintained to remove any remaining moisture and low and high boilingvolatiles, air toxics (including mercury, arsenic, and some sulfuroxides) are removed. The third zone is a cooling zone where the coal iscooled in a controlled atmosphere. Cooling is conducted at a rate whichdoes not compromise the structural integrity of the coal. After exitingfrom zone 5, the product coal typically has a moisture content <2% and avolatile content between 5-15%. These two parameters may be varied tosuit utility requirements by altering processing conditions.

A gas collection manifold in each chamber captures all moisture andvolatile matter released from the coal during processing. A gasseparator separates the light hydrocarbons that are directed back to theburners that heat the zones. Heavier gases separated from the lightergases are collected in a separate vessel for subsequent sale orconversion to synthetic fuels and chemical feed stocks.

The processing plant has been designed to improve the quality of minedcoal by approximately 30%, depending on the quality of the incomingcoal. This is achieved through the removal of both surface and inherentmoisture plus volatile matter from within the coal. This volatile mattercontains most of the contaminants and, once removed, leaves theremaining coal to burn cleanly. The process is designed to utilize aminimum amount of energy and time to improve the coal in a safe andconsistent manner.

The facility includes a seven day storage capacity of coal in both theraw and finished coal piles. The coal feed stock is delivered to thefacility and shipped from the facility by truck or rail. The incomingtrucks or rail cars proceed to an unloading station where the contentsare dumped into a receiving bunker. Coal from the bunker is conveyed toa stacker where the coal is distributed and packed into a storage pile.

A coal reclaimer harvests coal from the storage pile and conveys it to aconveyor/tripper located above the in-process storage silos. The storagesilos store approximately 2.5 hours worth of coal for each processingunit. The conveyor/tripper delivers coal to the silos on a continuousbasis. After the coal is processed, it is delivered to the processedcoal conveyor at a temperature of 200° F. and conveyed to the finishedproduct stacker where it is compacted and stored in the processed coalpile. From the processed coal pile, the coal is reclaimed and conveyedto rail cars for shipment.

All gasses generated by the different process units are sent to acentral gas processing unit where heavy hydrocarbons are separated andcondensed into a liquid that is stored and shipped by rail to an oilrefinery for further processing. The remaining gasses are separated andfour main streams are generated. The first gas stream is carbon dioxidethat is recycled back to the coal processing units; the second streamconsists of methane and ethane and is sent back to the coal processingunits and used as a fuel to heat the coal. The third stream is propanewhich is condensed and stored as a liquid both for start up of theinventive process and for back up for the fuel gas system. A propane/airmixer produces a fuel gas equivalent BTU mix. The fourth gas streamconsists of pentanes and heavier hydrocarbons and is condensed andshipped to a refinery via truck for further processing or sale.

The facility includes coal handling equipment to receive, store andreclaim the coal from a coal feed stock pile for processing. The coal isdelivered to in-process storage bunkers located above the processingequipment. From the storage bunkers the coal flows by gravity into theprocess equipment and is fed into chutes by a series of screw conveyorsthat deliver a full width layer of coal to the processing equipment. Theprocessing equipment consists of a series of vibratory feeders thatconvey a 4-inch deep bed of coal through the two heating chambers orzones and the cooling chamber or zone as described above.

In the first heating chamber, the coal is preferably heated from ambientto a temperature of 400° F. or more. The heating occurs under a blanketof carbon dioxide. Hot carbon dioxide is supplied to the first heatingchamber through a fluidized bed built into the bed of the vibratoryfeeder. The carbon dioxide picks up moisture and some hydrocarbon gassesand delivers them to the gas cleaning module for separation of dust andmoisture and further processing.

The coal is delivered to the second heating chamber where gas firedheaters heat the coal from 400° F. to 1500° F. or more. Carbon dioxideis fed above the bed of the vibratory feeder. The carbon dioxide picksup additional moisture and a larger amount of hydrocarbon gasses. Thegas mixture is delivered to the gas cleaning module for furtherprocessing.

The cooling chamber consists of a vibratory feeder moving the coal fromone end of the vibratory feeder to the other while being exposed to astream of cool carbon dioxide that has been fed into the unit. Carbondioxide is reclaimed from the process at the gas cleaning module.

Carbon dioxide recycled and cooled from the first heating chamber whichhas been cooled and de-humidified is supplied to this cooling chamberthrough a fluidized bed built into the bed of the vibratory feeder. Theexhaust gasses from the cooling chamber are heated and re-circulated tothe first heating chamber, thereby recycling the heat.

BRIEF DESCRIPTION OF THE DRAWINGS

Various other features of the invention will become apparent to thoseskilled in the art from the following discussion taken in conjunctionwith the appended drawings in which:

FIG. 1 is the primary schematic diagram of the process showing theproduct flow through the facility, partial circulation of carbon dioxidethrough the process, and the gas separation unit that receives andseparates by-products of the process.

FIG. 2 is a cross sectional view of the first heating chamber or zone.

FIG. 3 is a cross sectional view of the second heating chamber or zone.

FIG. 4 is a cross sectional view of the cooling chamber or zone.

FIG. 5 is the secondary schematic diagram showing the thermal trail ofthe carbon dioxide through the process facility.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As required, detailed embodiments of the present invention are disclosedherein; however, it is to be understood that the disclosed embodimentsare merely exemplary of the invention which may be embodied in variousforms. Therefore, specific structural and functional details disclosedherein are not to be interpreted as limiting, but merely as a basis forthe claims to be appended later and as a representative basis forteaching one skilled in the art to variously employ the presentinvention in virtually any appropriately detailed structure.

Reference will be made herein to the drawings in which likecharacteristics and features of the present invention shown in thevarious figures are designated by the same reference numerals.

The apparatus includes three chambers, each of which is considered azone. Coal is gradually heated in the first two chambers (zones) andthen cooled in the last chamber (zone). Each heating zone may be viewedas a stand-alone partial gasification chamber. Coal is heated undercontrolled temperatures, residence time, and ambient pressure as itprogresses through each zone. Process variables in each zone areadjusted to suit desired end product specifications.

Coal is first crushed and graded using conventional crushing machines,i.e. a Gundlach double roll crusher or a McClanahan type crusher toreduce the feedstock to an average 90% passing 2 inches. It is thenscreened to remove any—¼″ aterial and transferred via a bucket conveyorto zone 1. Zone 1 contains a vibratory bed that moves the coal along ata controlled rate to match the residence time for this zone. Thevibratory bed is heated with hot carbon dioxide that is fed in from thebottom of the bed. The temperature of zone 1 is maintained at around400° F., which removes most of the surface moisture from the coal.

At the end of the bed, the coal is deposited onto the second vibratorybed (zone 2) via a chute utilizing gravity to save energy. As coalenters zone 2, it is heated by gas fired heaters that maintain thetemperature of the zone at about 1500° F. Coal passes through this zonefor a few minutes to remove any remaining moisture and any low-boilingvolatile matter from the coal. The retention time of the coal in zones 1and 2 varies depending upon the initial moisture and volatile content ofthe coal feed and the desired moisture/volatile content of the finalproduct. Typical residence times are on the order of 3-5 minutes perzone.

The coal in the second heating chamber (zone 2), is heated by a seriesof gas fired heaters to temperatures as high as 1,500° F. The carbondioxide fed into zone 2 picks up additional moisture and the remainingheavier volatile gases emanating from the coal. This gaseous mixture iseventually delivered to the gas separation section. Between zones 1, 2,and 3, the coal loses the bulk of its volatile matter and undergoes someshrinkage as it losses a portion of its mass. Typically, weight loss isin the range of 15-35% of the coal's initial mass, but weight loss islargely dependent upon the characteristics of the feed coal, zonetemperature, residence time, and other factors. These influencingfactors are integrated into the overall process control system thatmonitors these parameters and adjusts them accordingly to obtain thedesired final product.

Control of the gaseous mixture inside each zone is critical to thesuccessful operation of the process. When coal is heated to the abovementioned temperatures, its moisture and volatile matter are driven offfrom the coal macerals. The expansion of the volatile matter atincreasing temperature creates fissures and voids within the coalstructure. If expansion is too rapid, these fissures can split the coaland the entire coal undergoes size degradation. Other undesirablecharacteristics are moisture re-absorption and spontaneous combustionafter the coal reaches ambient temperature. However, the inventiveprocess monitors the gaseous mix inside each heating zone to control therate of removal of these volatile elements.

This is accomplished by creating a dynamic phase equilibrium between thesolid/liquid and gaseous forms of the volatile matter inside the coalvia an inert atmosphere created in part by the volatized materials fromthe coal and the introduction of an external, non-oxidizing, inert gassuch as carbon dioxide or nitrogen. The chambers are provided with entryand exit ports for the admission and retrieval of such gases. Theresidence time, the type, and individual amounts of gasses circulatedwithin each zone are predetermined for each feed coal and used ascontrol parameters in the process. The oxygen content of the gasseswithin each zone is typically less than 2% oxygen.

Another effect of the atmosphere provided within each zone is to ensurethat the coal maintains most of its natural structural integrity andresists the tendency to disintegrate into fines (particles less than1/e), even though the coal may be more fragile due to some loss of mass.The processed coal is ready for transfer by a chute using a gravity feedto the cooling zone (zone 3). The gravity feed saves energy.

In zone 3, the coal is cooled by exposing it to a dry inert gas that isfree of oxygen. In the process design, the cooling chamber (zone 3)consists of a vibratory feeder moving the coal from one end of thevibratory feeder to the other while being exposed to a stream of coolcarbon dioxide that has been reclaimed from the process at the gasseparation section. This carbon dioxide is recycled from zone 1 after ithad been cooled and de-humidified and supplied to zone 3 through afluidized bed built into the bed of the vibratory feeder. The exhaustgasses from the cooling section are heated and re-circulated to zone 1.Control systems ensure that the cooling stream of carbon dioxide onlycontains 0.25 to 0.75% oxygen, by volume, with a moisture content ofless than 1% by weight, and flows counter current to direction of flowof the coal.

From zone 3, the coal is now ready for shipment to utility andindustrial markets. If needed, fines may be removed from the coal byscreening so that the finished product has a size range of ¼″ to 2″.

The fines are optionally converted into briquettes for home use or usedas fuel to supply heat for the process. Alternatively, the fines aresold to a third party for processing into briquettes for home use. Theend result is the production of clean burning, low smoke coal briquettesthat have strong structural make up, moisture resistant, long shelf lifeand are cost effective.

What follows is a description of the individual pieces of equipment. Thevibratory feeders are, for the most part, standard pieces of equipmentdesigned to move solid products by inducing vibration on a flat bed.Because of the high temperatures involved in the process, the vibratingbeds are lined with refractory materials. The vibrating bed is mountedon springs and the vibration is generated by an eccentric arm mounted ona shaft and driven by an electric motor. The electric motor iscontrolled by a variable frequency drive in order to modulate the speedof the conveyor. The vibratory feeder bed is provided with a metal skirtthat is immersed in a sand seal in order to prevent the carbon dioxideatmosphere inside the enclosure from escaping.

The heaters comprise natural gas burners mounted on the walls of thechamber. The fuel/air mixture is controlled to maintain a constant exittemperature. As the amount of combustible gas produced by the processincreases within the chamber, the external gas feed to the burner isreduced and combustion air is controlled to sustain combustion andmaintain the exit temperature of the gas. Any excess hydrocarbons beinggenerated by the process are carried by the carbon dioxide to thechemical section for processing.

Heat, from external sources, is supplied to the process in threediscrete, independent locations. All heat addition locations utilizepropane as the start up fuel, produced by the gas plant installed as apart of the process. Propane is stored at the facility.

The first heat addition location is the CO2 fired heater which raisesthe temperature of the CO2 stream going to first heating chamber. Thisfired heater raises the CO2 from an inlet temperature of 522° F. to aCO2 discharge temperature of 938° F. A burner utilizingpropane/ethane-methane as the burner fuel provides the necessary heat.The burner is equipped with both a vendor furnished Combustion ControlSystem (CCS) and Burner Management System (BMS).

The burner temperature profile and consequently the burner heat releaseare chosen such that the requisite CO2 temperature rise can be achieved.Given the relatively high CO2 inlet temperature, the flue gas exhausttemperature out of the fired heater is also elevated. A flue gas tocombustion air heat exchanger is installed to preheat burner combustionair with the flue gas exiting the fired heater to reduce burner fueldemand. An un-insulated metal stack is installed downstream of thecombustion air preheater to discharge the flue gas to ambient.

The second heat addition location is the gas fired heater heating thecoal going to the second chamber. This fired heater raises the incomingcoal from the first chamber to a coal discharge temperature of 1500° F.Burners fueled with propane/ethane-methane provide the necessary heat.The burners are also equipped with a vendor furnished Combustion ControlSystem (CCS) and BMS. The burner temperature profile and consequentlythe burner heat release are chosen such that the requisite CO2temperature rise can be achieved. Given the high flue gas exittemperature, the system includes a flue gas to combustion air heatexchanger to raise incoming combustion air temperature. An un-insulatedmetal stack is installed downstream of the combustion air preheater todischarge the flue gas to ambient. One of the main advantages of theprocess is that it recycles 100% of the heat removed from the coalduring the cooling process to heat the first heating section of theprocess.

Centrifugal fans are utilized to move the process gas through thesystem. The fans are of the radial blade type and, in some cases, aremade from specialty metals to handle the high temperatures and corrosivenature of the gasses being conveyed.

The dust collector is utilized to separate any dust from the process gasand water vapor being generated in the first heating chamber. The dustcollector is of the bag type and the bags are made of material suitablefor temperatures up to 400° F. Normally, compressed air is utilized toshake the bags but in this case carbon dioxide is utilized in order tokeep an oxygen starved atmosphere in the process. Because of the hot,humid and corrosive environment, all internal parts in contact with theprocess stream are made of stainless steel.

The water separator consists of a finned water coil with a large drainpan that condenses the moisture from the process gas stream and drainsit. Cooling water for the coil is provided by a condenser water systemconsisting of cooling towers and circulating pumps.

The cooling towers are the counterflow type and are sized to cool waterfrom 115° F. down to 85° F. at an ambient wet bulb of 78° F. Thecondenser water system provides cooling to the coal processing as wellas the gas processing side of the system. Cooling tower fans utilizeelectrical reversing relays to reverse rotation on the fans in case oficing during winter.

The condenser water pumps are of the vertical turbine type and arelocated in a wet well at the cooling tower structure where the watercooled by the towers is collected. The pumps discharge water into apiping system that conveys the water to cooling coils and heatexchangers throughout the facility. The pumps are controlled by variablespeed drives to control the amount of water flowing through the systemand minimize energy consumption in winter.

Metal chutes conveying coal from one area of the process to another arelined with refractory materials suitable for handling coal as well asthe temperatures generated by the process. Vibratory feeders are housedinside refractory enclosures that are under a slight negative pressuregenerated by the fans exhausting the gasses from the enclosure. Thecarbon dioxide atmosphere of course prevents the coal from igniting inthe presence of oxygen above 400° F.

The gas by-products from the coal heating chambers consist of thosematerials contained in the combined streams exiting the first and secondchambers. These are the volatiles driven from the coal at the varioustemperature levels and the gas that is being used as a heat transfermedium being used to heat and cool the coal at various stages. The heattransfer gas is carbon dioxide, but nitrogen is also contemplated.

At the low temperature level, i.e. 400° F., volatiles consist primarilyof surface moisture. At 1500° F., the volatiles consist of moisturewithin the coal and light hydrocarbons, hydrogen, carbon dioxide, carbonmonoxide, hydrogen sulfide, and ammonia. At the highest temperatures,heavier hydrocarbon, liquids are driven off. Much of the hydrocarbonsare deficient in hydrogen, consisting of alkenes and aromatics. Inaddition to hydrocarbons, the volatiles consist of such contaminantinorganics that are released at higher temperatures, i.e. 2,000° F. Suchinorganic contaminants consist of chlorine, mercury, arsenic, etc.

The purpose of the gas module is to remove contaminants and separatevarious components into saleable and transportable products. Theseproducts will be discussed in the products section. Another importantpurpose is to separate carbon dioxide for recycle back to the coaldrying section for its use as a heat medium. Of critical importance tothe design of the gas plant is the composition of the volatiles drivenfrom the coal at the various stages of the cleaning process.

The following are the products from the gas plant:

Fuel gas. This consists of C4-material, i.e., methane, ethane, ethylene,butanes, and butylenes. This is used in the coal plant burners as fuelgas. This gas is amine treated, and is relatively free of H2S.

Propane, propylenes. The coal plant requires a source of fuel forstartup. For this reason, C3s separation and storage is provided. ExcessC3s above that required for the coal plant startup is sold, such as to arefinery as feedstock to a refinery Alkylation unit.

Butanes, butylenes. This is a liquid product stream, and storagefacilities are provided. This is optionally used as fuel or as a productto be sold, such as to a refinery as feedstock to a refinery Alkylationunit.

Heavy Liquid, C5 plus liquid. This is described in more detail below.

Sulfur. Described below.

CO2. CO2 is a makeup to the inert gas which is used as a heating mediumin the coal cleaning section.

CO. Carbon monoxide is widely used in the chemical industry as thematerial to produce polyurethane or polycarbonate.

Individual processes are:

Contaminant Removal.

Solid adsorbents remove vapor contaminants such as mercury from gas tovery low levels. This is accomplished with two or more adsorbentvessels. As one adsorbent vessel has filled with contaminants, it isbrought offline to have the spent adsorbent replaced with freshadsorbent. Solid contaminants such as arsenic are removed from theliquids thru filtration.

Hydrocarbon Treating.

The removal of H2S from fuel gas is accomplished via amine treating. Inthis process, H2S is absorbed from the gas in an adsorption column by aspecific type of amine. The purified gas is then sent to furtherprocessing or used as fuel gas. The H2S absorbed by the amine is thensent to a stripping column were H2S is driven off as a concentratedstream. The lean amine is then recycled back to the absorber. The H2Sstripped from the amine is then sent to a sulfur recovery unit.

CO2 Removal.

Removal of CO2 is by 2^(nd) stage amine separation. The amine that wasused for H2S removal was selective for H2S, leaving CO2 in the gas.

CO Removal.

Carbon monoxide is captured in a process involving absorption/desorptionusing a solvent containing cuprous aluminum chloride in toluene.

Water Removal.

Water is collected from various locations within the gas plant. Theseinclude the adsorbent driers, water boots from the separators. The wateris sour, and consequently is treated in a sour water stripper. H2S andammonia dissolved in the water is stripped and combined with the acidgas from the amine treater, and together sent to sulfur recovery.

The treated gas containing C4 minus material is sent to the light gasseparation section. In this section, methane/ethane is first separatedusing a refrigerated J-T process. This includes an adsorbent dehydrator,propane chiller, cold separator, and de-ethanizer column operating at−30° F. The bottoms product from the de-ethanizer is sent to adepolarizer and debutanizer where propanes/propylenes andbutanes/butylenes are separated, respectively. The bottoms product fromthe debutanizer contain the C5 plus hydrocarbons which combine with themain separator liquid and sent to liquid product storage for subsequentsale.

The heavy liquid (C5 plus material) consists of a wide boiling rangematerial ranging from light naphtha to diesel and heavier. It ishydrogen deficient and highly aromatic. It contains oxygen bearinghydrocarbons such as ethers, aldehydes, esters, and ketones. It is astabilized material suitable for storage and transportation to apetroleum/petrochemical refinery for further processing. To avoid gumformation, it is stored in a relatively air free environment, that beingan insulated, gas blanketed storage tank.

A final by-product is sulfur. It is captured from the H2S that isproduced in the sour water stripper and amine units of the gas plant,and processed in a Claus unit to produce elemental sulfur. The Clausunit produces sulfur by reacting H2S over a catalyst with air. Thereaction is highly exothermic, resulting in production of high pressuresteam generated in a waste heat boiler. This steam is integrated inother sections of gas plant and used for heating. The excess steam couldalso be used with a turbine to generate electricity.

Sulfur is stored and transported both as a liquid and solid. It is asolid when cooled and formed into briquettes that are more easilytransported to facilities for further processing, i.e., fertilizer,sulfuric acid, etc.

Turning finally to the drawing, FIG. 1 is the primary schematic diagramof the process showing the product flow through the facility, partialcirculation of carbon dioxide through the process, and the gasseparation unit that receives and separates by-products of the process.

The schematic of the process is shown generally at 10. Raw coal 12 thathas already been crushed to size and graded elsewhere at the facility(not shown) is loaded into a hopper/feeder 14. It is then fed at 16 tothe first zone chamber 18 where it is heated to 400° F. using hot carbondioxide gas that enters the chamber 18 at 20. This drives off moisture,which is carried out of the chamber 18 by the exiting carbon dioxide at22.

The 400° F. temperature coal then exits the chamber 18 at 24 and movesto the second zone chamber 26. There is heated to 1500° F. using gasfired burners described in connection with FIG. 3. At this temperature,by-products are driven out of the coal in the form of volatile matterThe volatile matter passes to a gas separation unit 28 at 30. It iscarried there by carbon dioxide that enters second zone chamber 26 at32.

In the gas separation unit 28, various by-products are separated fromeach other and discharged into different streams. The first such streamis methane and ethane at 34. The methane and ethane is recycled at 36back to second zone chamber 26 where it is burned in gas fired burnersto heat the coal to 1500° F. in an oxygen free environment. Thus thefirst by-product at least partially fuels the inventive process, whichwas not taught by Hunt, the primary prior art reference. The secondstream is propane at 38. At least some of the propane produced by theprocess is stored at the facility because it is used for heating atstartup. Left over amounts can be sold as a by-product of the process.The next stream is heavy carbons at 40 which can be sold to others forchemical feedstocks. The penultimate stream is pentane and heavierhydrocarbons at 42, also saleable to others. The final stream 44 is toseparate out the carrier carbon dioxide for recycling back at 32 tosecond zone chamber 26

The coal heated to 1500° F. in second zone chamber 26 exits that chamberat 46 and passes to third zone chamber 48, where it is cooled in a dryand oxygen free environment. The carbon dioxide that carries moistureout of the first zone chamber 18 at 22 is directed to gas cleaningmodule 50, where the carbon dioxide is dehumidified. After some othersteps described in connection with FIG. 5, the carbon dioxide entersthird zone chamber 48 at 52, where it is used to cool the coal down toabout 200° F. Then the cleaned coal is discharged at 54 from the processfor storage and delivery to users. The carbon dioxide, which is heatedby cooling the coal in third zone chamber 48 exits that chamber at 56and is returned at 20 to the first zone chamber 18 to heat the coaltherein to 400° F. as described earlier.

FIG. 2 is a cross sectional view of the first heating chamber or zone18. Coal 12 enters the chamber 18 at 16 and is moved on a vibratoryfeeder 58 which includes a fluidized bed 60. Hot carbon dioxide entersat 20 and is fed into the fluidized bed 60 to heat the coal and absorbthe moisture. The dried coal heated to 400° F. then exits first zonechamber 18 at 24 enroute to the second zone chamber 26 as seen in FIG.3. The carbon dioxide and moisture combination exit at 22 enroute to thegas cleaning module 50 as seen in FIG. 1.

FIG. 3 is a cross sectional view of the second heating chamber or zone26 into which coal 12 enters at 24 and is moved on vibratory feeder 58which includes fluidized bed 60. In this chamber, the coal 12 is heatedto 1500° F. by gas fired burners 62. Carbon dioxide enters the chamber26 at 32, picks up by-products given off the coal 12 by the 1500° F.temperature, and leaves zone 26 at 64 enroute to the gas separation unit28 seen in FIG. 1. The 1500° F. temperature coal leaves zone 26 at 46enroute to the third zone 48 seen in FIG. 4.

FIG. 4 is a cross sectional view of the cooling chamber or third zone48. Coal at a temperature of 1500° F. enters the third zone 48 at 46.Coal 12 is moved on vibratory feeder 58 which includes fluidized bed 60.Carbon dioxide, which has been cooled by the apparatus described inconnection with FIG. 5, enters zone 3 at 52. The cooled carbon dioxideis fed to the fluidized bed 60, and cools the coal 12 to 200° F., atwhich temperature combustion cannot occur when the coal is again exposedto oxygen. The coal 12 then exits the cooling zone 48 at 54 for storageand shipment to users. The carbon dioxide is, of course, heated in thecourse of cooling the coal, reaching a temperature 522° F. The heatedcoal exits cooling zone 48 at 56.

FIG. 5 is the secondary schematic diagram showing the thermal trail ofthe carbon dioxide through the process facility. The carbon dioxideheated to 522° F. in the cooling zone 48 exits that zone at 56. It isthen directed to a CO2 gas fired burner 66 which raises the temperatureof the CO2 to 938° F. The gas fired burner 66 utilizespropane/ethane-methane as the burner fuel. The carbon dioxide at atemperature of 938° F. is then directed at 20 to the first zone 18 whereit is used to heat incoming raw coal 12 to 400° F. as described earlierin connection with FIG. 2. This results in conservation of energybecause a substantial amount of the heat of the process obtained fromcooling the coal in the cooling zone 48 is recycled into heatingincoming raw coal in the first zone 18.

The carbon dioxide thereafter exits the first zone 18 at 22 and then issent to a dust collector 68 to be cleansed of dust for later use in theprocess. The carbon dioxide leaves the dust collector at 70 usingcentrifugal fan 72, and is sent to a counterflow heat exchanger 74 whichit enters at 76. The heat exchanger 74 is used to cool the carbondioxide for later use in the cooling zone 48.

The heat exchanger 74 receives cooled water from a cooling tower 78.Cooled water is maintained in a reservoir 80 and is sent to the heatexchanger 74 using pump 82. Cooled water enters the heat exchanger at 84and leaves it at 86. The water is warmed in the heat exchanger 74 bycooling the carbon dioxide. The warmed water is then directed to thecooling tower 78 where it passes through spray nozzles 88 and film file90 to be cooled again. It then returns to reservoir 80. The cooledcarbon dioxide exits the heat exchanger 74 at 92 and sent usingcentrifugal fan 94 to the cooling zone 48 which it enters at 52 to coolthe coal from 1500° F. to 200° F. as described previously in connectionwith FIG. 4.

While the invention has been described, disclosed, illustrated and shownin various terms or certain embodiments or modifications which it hasassumed in practice, the scope of the invention is not intended to be,nor should it be deemed to be, limited thereby and such othermodifications or embodiments as may be suggested by the teachings hereinare particularly reserved especially as they fall within the breadth andscope of the claims hereto appended.

1. A coal enhancement process to increase its rank comprising: heating coal in a substantially oxygen free atmosphere in at least one zone to remove moisture and drive off by-products to increase coal rank; cooling coal in a substantially oxygen free atmosphere in another zone; collecting the enhanced coal; and recycling some of the by-products as fuel to heat the coal and conserve energy.
 2. The process of claim 1 which further comprises dividing the heating of the coal into two zones, the first heating to approximately 400° F. to remove surface moisture, and the second heating to approximately 1500° F. to remove more moisture and by-products.
 3. The process of claim 1 which further comprises separating out by-products not recycled and collecting same for productive use elsewhere.
 4. The process of claim 2 which further comprises cooling the coal using carbon dioxide cooled using a cooling tower, and recycling the heat removed from the coal to heat incoming coal in the first zone to remove surface moisture.
 5. The process of claim 1 in which the by products comprise methane and ethane, propane, heavy carbons, pentane and heavier hydrocarbons, and the process further comprises: recycling the methane and ethane from a gas separation unit to a heating zone to use as fuel in heating the coal after start-up of the process; and recycling propane produced earlier by the process to use as fuel in starting up the process.
 6. The process of claim 1 which further comprises using carbon dioxide as inert gas to create the substantially oxygen free atmosphere.
 7. The process of claim 3 in which the carbon dioxide is used as a carrier to entrain moisture and entrain by-products in the heating phase to carry them to a gas separation unit where it is separated from the by-products, dehumidified in a gas cleaning module, passes through a heat exchanger to be cooled using water from a cooling tower, used in the cooling zone to cool coal where it is heated in so doing, and is recycled back to the heating phase to assist in heating incoming coal again.
 8. The process of claim 1 in which driving off the by-products by heating the coal reduces the weight of the coal while increasing its rank, wherein the reduced weight of the coal reduces energy costs in transporting the enhanced coal to a user thereby conserving energy.
 9. The process of claim 1 in which driving off the by-products reduces release of pollutants when the coal is burned.
 10. The process of claim 1 in which driving off the by-products reduces the amount of smoke produced by burning the coal.
 11. A coal enhancement process to increase its rank comprising: heating coal in an inert substantially oxygen free atmosphere in a first zone to approximately 400° F. to remove surface moisture; heating coal in an inert substantially oxygen free atmosphere in a second zone to approximately 1500° F. to drive off more moisture and drive off by-products to increase coal rank; cooling coal in an inert substantially oxygen free atmosphere in a third zone; collecting the enhanced coal; recycling some of the by-products as fuel to heat the coal and conserve energy; separating out remaining by-products from the coal and from each other; collecting the separated out by products for productive uses elsewhere; and recycling heat removed from the coal in the third zone to the first zone to heat the coal to 400° F. and conserve energy.
 12. The process of claim 11 in which the by products comprise methane and ethane, propane, heavy carbons, pentane and heavier hydrocarbons, and the process further comprises: recycling the methane and ethane from a gas separation unit to zone 2 to use as fuel in heating the coal to approximately 1500° F. after start-up of the process; and recycling propane produced earlier by the process to use as fuel in starting up the process.
 13. The process of claim 11 which further comprises using carbon dioxide as the inert substantially oxygen free atmosphere.
 14. The process of claim 13 in which the carbon dioxide is used as a carrier to entrain moisture in the first zone, passes through a dust collector to remove dust picked up in the first zone, is dehumidified in a gas cleaning module, is cycled into zone 2 to entrain by-products to carry them to a gas separation unit where it is separated from the by-products, passes through a heat exchanger to be cooled using water from a cooling tower, used in the cooling zone to cool coal where it is heated in so doing, and with supplemental heat added is recycled back to zone 1 to heat incoming coal and entrain moisture again.
 15. The process of claim 11 in which driving off the by-products by heating the coal to approximately 1500° F. in zone 2 reduces the weight of coal while increasing its rank, wherein the reduced weight of the coal reduces energy costs in transporting the enhanced coal to a user thereby conserving energy.
 16. The process of claim 11 in which driving off the by-products reduces release of pollutants when the coal is burned.
 17. The process of claim 11 in which driving off the by-products reduces the amount of smoke produced by burning the coal.
 18. The process of claim 11 in which increasing the rank of the coal is accomplished with a processing time of six to eighteen minutes. 